1. Industrial Field of the Invention
The present invention relates to a method and apparatus for manufacturing a magnetic core for use in a transformer, and more particularly, to a method and apparatus for manufacturing a magnetic core made from amorphous magnetic sheet materials.
2. Description of the Prior Art
An amorphous magnetic material used for a magnetic core of a transformer has usually a very small thickness of, for example, 0.022 mm to 0.025 mm. Thus, a predetermined number of the amorphous magnetic sheets are superposed to have a predetermined thickness and bonded to one another, prior to being formed into a shape of a magnetic core.
For example, U.S. Pat. No. 4,413,406 discloses a method of manufacturing a core of an amorphous transformer using low temperature metal for bonding in which a bonding process is performed by using a metal of a low melting point.
This U.S. patent relates to a method which comprises the steps of: supplying from a plurality of reels the amorphous metal sheets wound therearound through an uncoiler in such a state that exposed surfaces of the supplied metal sheets from the reels are extending opposite face to face with each other; interposing a bonding metal material having a melting point of 50.degree. C. to 350.degree. C. between the opposite adjacent sheets; superposing a plurality of the amorphous metal sheets to form a compound sheet; heating the compound sheet at a temperature not less than the melting point of the bonding metal material; cooling the compound sheet for solidifying the molten bonding metal material to bond the plurality of amorphous metal sheets; cutting the compound sheet by a predetermined length; winding the cut compound sheet to form a core; and forming the wound core into a rectangular shape.
The prior art mentioned above has problems as follows:
(1) The cost of the material and investment in manufacturing equipment are too expensive because indium, bismuth, lead, cadmium, tin and the like are used as a bonding metal and such metals of low melting point are heated to bond the amorphous metal sheets. These metals are often harmful to humans, which results in a problem of environmental contamination. PA1 (2) The conventional method requires some additional tedious steps of heating and cooling for the bonding material, so that the total number of the manufacturing steps is unnecessarily increased. PA1 (3) Because the amorphous metal sheets are wound in such a manner that the bonding metal is partially interposed between the adjacent amorphous metal sheets, there occurs gaps between the adjacent sheets to deteriorate a space factor. A magnetic characteristic is thus decreased. PA1 (4) In the conventional method, the amorphous metal sheets are formed into a core of a rectangular shape after they are once wound in a circular shape. The manufacturing steps are therefore increased in number. In this connection, a winding installment as well as a forming equipment are required for the manufacturing. And also, an installing space for this equipment is unfavorably enlarged. As a result, the manufacturing cost inevitably becomes high. PA1 (5) A large amount of energy is consumed in such heating and cooling processes. PA1 1. The obtained magnetic core is of a high closeness degree because the adjacent amorphous sheets can move freely during the forming step. Thus, the amorphous magnetic core is excellent in the magnetic properties. PA1 2. Because the cut amorphous sheets are directly formed in the rectangular shape at a normal temperature, any specific bonding material and steps for bonding are not required, which results in a reduction of a cost for manufacturing the magnetic core. Energy of a heating efficiency is unnecessary, so economical process can be achieved. Further, equipment for bonding and sheet-winding circularly are not required, so that the investment of the installment is conspicuously decreased and the installment occupation space can be reduced. PA1 3. The magnetic core can be manufactured only by the mechanical processing without using any toxic substances.
In view of the problems of the prior art, a primary object of the present invention is to provide a method and apparatus for manufacturing an amorphous magnetic core, by which an amorphous magnetic core having an improved closeness degree (in other words, the gap spaces in the core are reduced sufficiently in size) and an excellent magnetic characteristic can be obtained.
A second object of the invention is to provide a method and apparatus for manufacturing an amorphous magnetic core in which no bonding material is required, no heating energy for the bonding process is necessary, and in which the manufacturing process steps are reduced in number, thereby decreasing manufacturing and running cost.
A third object of the invention is to provide a method and apparatus for manufacturing an amorphous magnetic core in which heating, cooling and winding equipment is not required so that the installment occupation space can be minimized. The investment for the factory is thereby conspicuously decreased.
A fourth object of the invention is to provide a method and apparatus for manufacturing an amorphous magnetic core which can produce the amorphous magnetic core without using any harmful substances.
According to the invention, an amorphous magnetic core is manufactured by the steps of: uncoiling amorphous sheets from a plurality of reels around which the amorphous sheets are wound, respectively;
bringing the plurality of amorphous blank sheets into close contact with one another and cutting them in a superposed form by a predetermined length;
storing the cut amorphous sheets of a predetermined number in place, and supplying the stored amorphous sheets onto a rectangular mandrel;
directly forming the amorphous sheets of the predetermined number into a rectangular shape along a contour of the forming mandrel, thereby producing a rectangular magnetic core; and
annealing the obtained rectangular magnetic core.
According to another aspect of the invention, there is provided a manufacturing apparatus for an amorphous magnetic core that comprises:
uncoiler means including a plurality of reels around each of which an amorphous blank sheet is wound, for uncoiling the amorphous blank sheets from the respective reels;
cutter means for bringing the plurality of amorphous sheets supplied from the uncoiler means into close contact with one another and cutting them in a superposed form by a predetermined length;
supply means for storing the cut amorphous sheets of a predetermined number, and supplying the stored amorphous sheets onto a rectangular forming mandrel;
rectangularly forming means for directly forming the amorphous sheets of the predetermined number into a rectangular shape along a contour of the forming mandrel, thereby producing a rectangular magnetic core; and
means for annealing the rectangular magnetic core.
Advantageous effects of the present invention are as follows: